LONDON – Britain’s Conservative government on Tuesday approved an overdue, over-budget plan for a high-speed rail line linking London with central and northern England, despite opposition from environmentalists and lawmakers in his own party.

Prime Minister Boris Johnson, who has often enthused about large-scale building projects, said his Cabinet had given the “green light” to the project, known as High Speed 2 or HS2.

He acknowledged that the new railway had been plagued by bad management but said that did not detract from the “fundamental value” of building it.

“This country is being held back by our inadequate infrastructure," Johnson told lawmakers in the House of Commons.

“We can try to get by with the existing routes from north to south … or we can have the guts to take a decision, no matter how difficult and how controversial, that will deliver prosperity to every part of the country," he said.

Johnson acknowledged that there was widespread opposition to the plan, but said “every great infrastructure project is opposed at this critical moment."

First approved a decade ago, the project has been the subject of repeated delays and reviews. Trains were originally scheduled to begin running in 2026, but Johnson said Tuesday that services could start by 2030.

Johnson vowed to rein in costs, saying there would be changes to the way the project is managed and a minister would be appointed to supervise it full-time.

The first 140-mile (225-kilometer) stretch of the line will link London to Birmingham, England's second-largest city, with trains traveling up to 225 miles an hour (360 kph). A planned Y-shaped second section will then extend to the northern cities of Manchester and Leeds.

Opponents claim the plan is too expensive and will ruin tracts of picturesque countryside. The projected cost, estimated at 33 billion pounds in 2011, has soared to as much as 106 billion pounds ($137 billion).

Conservative lawmaker Michael Fabricant, who represents a central England district on the HS2 route, said the rail line would damage or destroy 100 ancient woodlands, causing “immense” environmental damage.

Green Party lawmaker Caroline Lucas said important wildlife sites and nature reserves would be “swept aside by the HS2 leviathan.”

“Our nature and wildlife is being wiped out at a terrifying rate and projects like HS2 add yet more harm,” she said.

But trade unions and industry groups welcomed the decision.

Railway Industry Association chief executive Darren Caplan said building HS2 would employ 30,000 people and when finished “could unlock a new golden age of rail."

Johnson, who won a large parliamentary majority in December’s election, has promised to build major new infrastructure projects t o better connect parts of the U.K. in the wake of Britain's divisive exit from the European Union. He also has vowed to boost regions outside the country'e economic hub of London and southeast England.

Johnson said Tuesday that HS2 would be just one part of a British “transport revolution” that would include thousands of new clean-energy buses and hundreds of miles of new cycle lanes, “with mini-Hollands blooming like so many tulips ."

Britain has an extensive but antiquated rail system that relies heavily on Victorian infrastructure. HS2 would be the first new railway built north of London for more than a century.

Britain lags behind European countries such as France and Spain when it comes to high-speed rail. Its only existing high-speed line is High Speed 1, completed in 2007, which links London to the tunnel connecting the U.K. and France under the English Channel.